Effect Of Soil Organic Carbon Research Articles

Effects of soil organic carbon (SOC) content and accessibility in subsoils on the sorption processes of the model pollutants nonylphenol (4-n-NP) and perfluorooctanoic acid (PFOA)

Subsoils control the release of hydrophobic pollutants to groundwater systems, but the role of subsoil soil organic carbon (SOC) in sorption processes of hydrophobic organic pollutants remains unclear. Thus, this study aimed to understand the role of subsoil SOC in sorption processes of 4-n-nonylphenol (NP) and perfluorooctanoic acid (PFOA) as model pollutants. To characterize the sorption behavior of NP and PFOA, 42 sub- and 54 topsoil samples were used for batch experiments. Differences in NP and PFOA sorption between sub- and topsoil samples and its mechanisms were identified using multiple regression analysis. Generally, the sorption of NP and PFOA was linear in all samples. The sorption of NP to soil samples (logKD = 1.78–3.68) was significantly higher and less variable than that of PFOA (logKD = −0.97–1.44). In topsoils, SOC content had the highest influence on NP and PFOA sorption. For NP, hydrophobic interactions between NP and SOC were identified as the most important sorption mechanism. For PFOA, hydrophobic as well as electrostatic interactions were determined depending on soil pH. In subsoils, the relevance of SOC content for pollutant sorption decreased drastically. For NP, not SOC content but rather SOC quality was relevant in SOC poor subsoils. For PFOA, clay and iron oxide content were found to be relevant for pollutant interactions with the solid phase. Thus, especially in SOC depleted subsoils, the sorption potential for PFOA remained unpredictable.

Effects of carbon on moisture storage in soils of the Wisconsin Central Sands, USA

Quantifying soil water storage is important for plant growth and agricultural production. This is particularly important in sandy soils because they are widely cultivated and prone to drought. We investigated the effect of soil organic carbon (SOC), soil texture and gravel content on soil moisture characteristics in sandy soils. Soil moisture characteristics were analysed using standard soil physical characterization as well as visible–near infrared (vis–NIR) spectroscopy and pedotransfer functions (PTFs). Volumetric water content (−10, −33, −1500 kPa) and available water capacity (AWC) increased by 0.01 to 0.02 m3m−3 with a 2% increase in silt plus clay content. Available water capacity increased by about 0.05 m3m−3 with a 1% increase in SOC. A 5% increase in gravel in the subsoil decreased the volumetric water content of the soil by 0.01 m3m−3. Predictions of volumetric water contents and AWC by vis–NIR were the best when using a random forest model. Pedotransfer functions for AWC predictions performed best when sand, silt, clay, bulk density and SOC were included. Soil moisture storage ranged from 44 to 65 mm in the top 50 cm. At mean evapotranspiration (4.2 mm day−1), irrigation requirements were reduced by 6 days in the sandy soils that have larger SOC and silt contents in the topsoil. These soils are sandy throughout but have subtle differences in particle‐size distribution, SOC concentrations and gravel content. These differences affect soil moisture storage considerably. Soil management practices that increase the SOC contents in these sandy soils favour moisture storage and tend to reduce irrigation requirements.Highlights SOC, soil texture and gravel affect soil moisture characteristics in sandy soils. With vis–NIR and PTFs, soil water storage, water characteristics and AWC in soils with >80% sand can be quantified and predicted. Available water capacity increased by about 0.05 m3m−3 with a 1% increase in SOC. Subtle differences in particle‐size distribution affect soil moisture storage and reduce irrigation requirements.

Global meta-analysis of the relationship between soil organic matter and crop yields

Abstract. Resilient, productive soils are necessary to sustainably intensify agriculture to increase yields while minimizing environmental harm. To conserve and regenerate productive soils, the need to maintain and build soil organic matter (SOM) has received considerable attention. Although SOM is considered key to soil health, its relationship with yield is contested because of local-scale differences in soils, climate, and farming systems. There is a need to quantify this relationship to set a general framework for how soil management could potentially contribute to the goals of sustainable intensification. We developed a quantitative model exploring how SOM relates to crop yield potential of maize and wheat in light of co-varying factors of management, soil type, and climate. We found that yields of these two crops are on average greater with higher concentrations of SOC (soil organic carbon). However, yield increases level off at ∼2 % SOC. Nevertheless, approximately two-thirds of the world's cultivated maize and wheat lands currently have SOC contents of less than 2 %. Using this regression relationship developed from published empirical data, we then estimated how an increase in SOC concentrations up to regionally specific targets could potentially help reduce reliance on nitrogen (N) fertilizer and help close global yield gaps. Potential N fertilizer reductions associated with increasing SOC amount to 7 % and 5 % of global N fertilizer inputs across maize and wheat fields, respectively. Potential yield increases of 10±11 % (mean ± SD) for maize and 23±37 % for wheat amount to 32 % of the projected yield gap for maize and 60 % of that for wheat. Our analysis provides a global-level prediction for relating SOC to crop yields. Further work employing similar approaches to regional and local data, coupled with experimental work to disentangle causative effects of SOC on yield and vice versa, is needed to provide practical prescriptions to incentivize soil management for sustainable intensification.

Roles of soil organic carbon and iron oxides on aggregate formation and stability in two paddy soils

Knowledges of aggregate stability and formation depending on soil organic carbon (SOC) and iron oxides are essential to the conservation of soil structure. In this work, the effects of SOC and different forms of iron oxides on the stability of aggregates of paddy soils were determined by applying the Le Bissonnais (LB) and extractions method by water, oxalate (OA), dithionite–citrate–bicarbonate (DCB), or hydrogen peroxide (H2O2). Two topsoils (0–20 cm) were selected based on two levels of SOC and iron oxides, high SOC (22.1 g kg−1)–low iron oxides (S1) and low SOC (8.50 g kg−1)–high iron oxides (S2) paddy soils from subtropical China. For the fast-wetting (FW) test, the percentage of 2–0.25 mm (34.0%) and >2 mm (42.2%) aggregate fractions were highest in S1 and S2, respectively. Both the soils had a >2 mm fraction that was above 60% under the slow-wetting (SW) and stirring after prewetting (WS) test. The free Fe oxide (Fe(DCB)) could increase in aggregate stability when SOC contents were low in S2. All three chemical extractions considerably decreased the >2 mm fractions (35.5–87.5%), and consequently increased the <0.053 mm fractions. The S1 soil presented the lower mean weight diameter (MWD) after DCB extractions, whereas it was no significantly different after OA or DCB extraction in S2 soil, indicating that Fe(DCB) had a greater effect on the stability of aggregates than amorphous Fe oxide (Fe(OA)) in the S1 soil, but both had the same effect for S2. The H2O2 treatment destructed>2 mm and 2–0.25 mm aggregates intensively, indicating that SOC was the major binding agent for aggregates of these sizes. The SOC was a key agent influencing soil aggregation not only in macro-aggregates (>0.25 mm) but also in micro-aggregates (0.25–0.053 mm) in the S1. The formation of aggregates in S1 was attributed to its higher content of organo-mineral complexes because the contents of SOC (3.30–11.2 g kg−1) were higher in >0.053 mm aggregates compared with S2 after H2O2 extractions. Fe oxides were the key agents for <0.25 mm aggregates formation. The MWD of the FW treatment was found to have a significant positive correlations with Fe(DCB), and MWD of the WS treatment proved significant positive correlations with SOC and Fe(OA) oxide, indicated that SOC and Fe oxides improved aggregate stability against external force collapse. This implies that the differential roles of SOC and Fe oxides in mechanisms of aggregate formation and stability in two paddy soils.

Simulation of Soil Organic Carbon Effects on Long-Term Winter Wheat (Triticum aestivum) Production Under Varying Fertilizer Inputs.

Soil organic carbon (SOC) has a vital role to enhance agricultural productivity and for mitigation of climate change. To quantify SOC effects on productivity, process models serve as a robust tool to keep track of multiple plant and soil factors and their interactions affecting SOC dynamics. We used soil-plant-atmospheric model viz. DAISY, to assess effects of SOC on nitrogen (N) supply and plant available water (PAW) under varying N fertilizer rates in winter wheat (Triticum aestivum) in Denmark. The study objective was assessment of SOC effects on winter wheat grain and aboveground biomass accumulation at three SOC levels (low: 0.7% SOC; reference: 1.3% SOC; and high: 2% SOC) with five nitrogen rates (0–200 kg N ha-1) and PAW at low, reference, and high SOC levels. The three SOC levels had significant effects on grain yields and aboveground biomass accumulation at only 0–100 kg N ha-1 and the SOC effects decreased with increasing N rates until no effects at 150–200 kg N ha-1. PAW had significant positive correlation with SOC content, with high SOC retaining higher PAW compared to low and reference SOC. The mean PAW and SOC correlation was given by PAW% = 1.0073 × SOC% + 15.641. For the 0.7–2% SOC range, the PAW increase was small with no significant effects on grain yields and aboveground biomass accumulation. The higher winter wheat grain and aboveground biomass was attributed to higher N supply in N deficient wheat production system. Our study suggested that building SOC enhances agronomic productivity at only 0–100 kg N ha-1. Maintenance of SOC stock will require regular replenishment of SOC, to compensate for the mineralization process degrading SOC over time. Hence, management can maximize realization of SOC benefits by building up SOC and maintaining N rates in the range 0–100 kg N ha-1, to reduce the off-farm N losses depending on the environmental zones, land use and the production system.

Erosion-induced carbon losses and CO2 emissions from Loess and Black soil in China

Soil erosion influences both lateral soil organic carbon (SOC) re-distribution and vertical soil CO2 emissions. While potential SOC mineralization during transport and the burial effects of SOC at depositional sites have been addressed in previous reports, erosion induced on-site CO2 emissions are still under-studied. In this study, two soils (Loess soil and Black soil) with similar texture but contrasting aggregate structure and SOC content were subject to a set of 60-min long simulated rainfall events. There were two different rainfall intensities (30 and 90 mm h−1) at three slope gradients (5°, 15° and 25°). Runoff and sediment from erosion plot were collected at 10-min intervals over 60 min. Soil CO2 emissions from eroding slopes, SOC and particle size distribution of the eroding soil were measured after the erosion events. The results show that the runoff rates from the two soils were comparable, but the sediment rates from the Loess soil roughly three times that from the Black soil. In general, the SOC erosion from the Loess soil was 1.8 times that from the Black soil, even though the SOC concentration in the original Black soil was 56% higher than the Loess soil. The cumulative soil CO2 emissions from the eroding slopes of the Loess soil ranged from 15.4 to 19.7 g C m−2, which was doubled on the Black soil (from 28.1 to 59.6 g C m−2). When the rainfall intensity raised from 30 mm h−1 to 90 mm h−1, the cumulative soil CO2 emissions from the Black soil decreased by 38.2%, but only declined by 10.0% on the Loess soil. When the slope gradient increased from 5° to 25°, the cumulative soil CO2 emissions decreased by 23.8% on the Black soil but by 12.6% on the Loess soil. Therefore, our observations suggest that the soil CO2 emissions on the Black soil was much more sensitive to the variations of rainfall intensity and slope gradients than the Loess soil. Greater SOC erosion should not be directly translated to less on-site soil CO2 emissions. The selective depletion/enrichment of SOC and the lability of individual components must be fully understood when accounting for slope-scale carbon balances.

Dynamic changes of polychlorinated biphenyls (PCBs) degradation and adsorption to biochar as affected by soil organic carbon content

Biochar amendment constitutes an effective soil remediation strategy for organic contaminants, but how the soil organic carbon (SOC) content affects polychlorinated biphenyls (PCBs) degradation and adsorption to biochar remains unclear. A 120-day biochar amendment experiment was conducted to investigate the dynamic effects of SOC on PCBs degradation in soil and adsorption to biochar. Biochar in low-SOC (LSOC) soils adsorbed a significantly higher amount of PCBs than did that in high-SOC (HSOC) soils. PCBs degradation was also greatly enhanced in LSOC soils when compared with that in HSOC soils after 30 days of biochar amendment. Degradation of di- and tri-chlorobiphenyls (CBs) were significantly enhanced in the LSOC soils than in the HSOC soils, while the biochar in the LSOC soil tended to adsorb significantly higher amount of tetra- and penta-CBs. Compared to biochar adsorption, microbial degradation contributed significantly to soil PCBs removal. Soil bacterial 16S rDNA abundance increased concomitantly with soil PCBs degradation. Regardless of SOC, soil bacterial communities and PCB congener compositions changed significantly after 30 days of biochar amendment. The abundance of Actinobacteria and Firmicutes were negatively correlated with the soil PCBs removal, while Gemmatimonadetes and Proteobacteria were positively correlated. The results of this study revealed that, compared with that to HSOC soils, biochar amendment to LSOC soils may have a greater positive effect on both soil PCB degradation and biochar adsorption. Therefore, the application of bamboo biochar to LSOC soils could be more effective than that to HSOC soils with respect to the remediation of PCBs contamination.

SOC Effects on Diethyl Phthalate Sorption to Four Soils in China

Purpose: Phthalate esters (PAEs) are commonly detected in agricultural soils of China, which can post potential threats to human health. Understanding their sorption to soils is important in assessing their transport and bioavailability in environment. Limited research focuses on the influence of soil organic carbon (SOC) on PAEs adsorption to soils at different depths and increased dissolved organic carbon (DOC) after adsorption. Materials and Methods: Batch sorption experiments of diethyl phthalate (DEP) to four types of soils were conducted in this study, including black soil, fluvo-aquic soil, paddy soil, and red soil. Total concentration of solute DEP and the concentration of free DEP not sorbed to DOC were measured with HPLC. The UV absorbance of supernatant was measured and specific UV absorbance at 254 nm was calculated for DOC aromaticity. Sorption isotherms of DEP to soil particles were fitted to the Langmuir model and the Freundlich model. Results and Discussion: Partial SOC can dissolve to DOC in solution, and 47.4- 89.4% of total DEP can be sorbed to DOC. Increasing DEP in solution can enhance aliphatic SOC dissolving. The sorption coefficients of DEP are higher to fluvo-aquic soils (Koc for surface soils 1820 L kg-1 and subsurface soils 1388 L kg-1) than to other soils (<520 L kg-1), which indicates that SOC fractions of different soils have varied affinity to DEP. Conclusions: SOC plays an important role in DEP sorption to soil particles. Soil samples from surface layers have higher affinity than those from subsurface layers. DOC from SOC in solution is important for DEP transport in soil, and organic pollution can accelerate SOC dissolving.

Soil Organic Carbon and Nitrogen Feedbacks on Crop Yields under Climate Change

Core Ideas SOC decline, due to increased temperatures, reduces wheat and maize yields globally. CO2 increase to 540 ppm partially compensates yield losses due to increased temperatures. Accounting for soil feedbacks is critical when evaluating climate change impacts on crop yield. A critical omission from climate change impact studies on crop yield is the interaction between soil organic carbon (SOC), nitrogen (N) availability, and carbon dioxide (CO2). We used a multimodel ensemble to predict the effects of SOC and N under different scenarios of temperatures and CO2 concentrations on maize (Zea mays L.) and wheat (Triticum aestivum L.) yield in eight sites across the world. We found that including feedbacks from SOC and N losses due to increased temperatures would reduce yields by 13% in wheat and 19% in maize for a 3°C rise temperature with no adaptation practices. These losses correspond to an additional 4.5% (+3°C) when compared to crop yield reductions attributed to temperature increase alone. Future CO2 increase to 540 ppm would partially compensate losses by 80% for both maize and wheat at +3°C, and by 35% for wheat and 20% for maize at +6°C, relative to the baseline CO2 scenario.

Latitudinal patterns and influencing factors of soil humic carbon fractions from tropical to temperate forests

Soil humic carbon is an important component of soil organic carbon (SOC) in terrestrial ecosystems. However, no study to date has investigated its geographical patterns and the main factors that influence it at a large scale, despite the fact that it is critical for exploring the influence of climate change on soil C storage and turnover. We measured levels of SOC, humic acid carbon (HAC), fulvic acid carbon (FAC), humin carbon (HUC), and extractable humus carbon (HEC) in the 0–10 cm soil layer in nine typical forests along the 3800-km North-South Transect of Eastern China (NSTEC) to elucidate the latitudinal patterns of soil humic carbon fractions and their main influencing factors. SOC, HAC, FAC, HUC, and HEC increased with increasing latitude (all P<0.001), and exhibited a general trend of tropical < subtropical < temperate. The ratios of humic C fractions to SOC were 9.48%–12.27% (HAC), 20.68%–29.31% (FAC), and 59.37%–61.38% (HUC). Climate, soil texture, and soil microbes jointly explained more than 90% of the latitudinal variation in SOC, HAC, FAC, HEC, and HUC, and interactive effects were important. These findings elucidate latitudinal patterns of soil humic C fractions in forests at a large scale, and may improve models of soil C turnover and storage.

Effect of Soil Organic Carbon on Perviousness and Conservation Property of Soil

This study was carried to use organic based wastes, as a source of soil organic carbon (SOC) to artificially restore the SOC in soils and explore its effects on Soil perviousness and conservation property. This property is defined by the author to represent the combined effect of the factors like SOC, porosity (Po), infiltration (In), erosion (Er) and runoff (Ru). The SOC was quantified in humus, pressmud, bagasse ash and fly ash, which were used as amendments for the four soils namely black cotton (BC), red, marshy and mountainous soils that prevail in the study area. The experiments were designed based on Response surface methodology with central composite design with respect to soil perviousness and conservation property. Quadratic models were developed to correlate soil-amendment combinations for the factors. For each soil a polynomial equation was built by combining all the factors for this soil property. Fly ash for BC soil, bagasse ash for red, marshy and mountainous soil were found to be the best suited soil-amendment combinations in enhancing the property of soil conservation and perviousness. The optimum SOC dosages were 1.005, 0.72, 0.76, and 0.86 g/g of BC, red, marshy and mountainous soils respectively.

Life cycle assessment of castor-based biorefinery: a well to wheel LCA

Diminishing fossil resources and environmental concerns associated with their vast utilization have been in focus by energy policy makers and researchers. Among the different scenarios put forth to commercialize biofuels, various biorefinery concepts have aroused global interests because of their ability in converting biomass into a spectrum of marketable products and bioenergies. This study was aimed at developing different novel castor-based biorefinery scenarios for generating biodiesel and other co-products, i.e., ethanol and biogas. In these scenarios, glycerin, heat, and electricity were also considered as byproducts. Developed scenarios were also compared with a fossil reference system delivering the same amount of energy through the combustion of neat diesel. Life cycle assessment (LCA) was used to investigate the environmental consequences of castor biodiesel production and consumption with a biorefinery approach. All the input and output flows from the cultivation stage to the combustion in diesel engines as well as changes in soil organic carbon (SOC) were taken into account. Impact 2002+ method was used to quantify the environmental consequences. The LCA results demonstrated that in comparison with the fossil reference system, only one scenario (i.e., Sc-3 with co-production of significant amounts of biodiesel and biomethane) had 16% lower GHG emissions without even considering the improving effect of SOC. Moreover, resource damage category of this scenario was 50% lower than that of neat diesel combustion. The results proved that from a life cycle perspective, energy should be given priority in biorefineries because it is essential for a biorefinery to have a positive energy balance in order to be considered as a sustainable source of energy. Despite a positive effect on energy and GHG balances, these biorefineries had negative environmental impacts on the other damage categories like Human Health and Ecosystem Quality. Although biorefineries offer unique features as promising solutions for mitigating climate change and reducing dependence on fossil fuels, the selection of biomass processing options and management decisions can affect the final results in terms of environmental evaluations and energy balance. Moreover, if biorefineries are focused on transportation fuel production, a great deal of effort should still be made to have better environmental performance in Human Health and Ecosystem Quality damage categories. This study highly recommends that future studies focus towards biomass processing options and process optimization to guarantee the future of the most sustainable biofuels.

Optimal organic carbon values for soil structure quality of arable soils. Does clay content matter?

Most soil structure-related physical properties are correlated to soil organic carbon (SOC) content. Texture, mineralogy, and SOC:clay ratio are also acknowledged to affect physical properties, however there is no consensus or general conclusions in this respect. Against this background, the present study aims at determining objectives for the management of SOC in terms of structural quality of agricultural soils. The large area in which 161 free-to-swell undisturbed samples were obtained for this research represents a major part of the Swiss agricultural land and belongs to one broad soil group (Cambi-Luvisols). The structural quality was scored visually, and bulk volumes (inverse of bulk density) were measured at standard matric potentials. To define the effect of SOC without interference of soil mechanical degradation, soils with good structural quality scores were considered first in studying the relationship between SOC and soil pore volumes. Results suggest that the relationship is always linear, irrespective of the clay content of the soils. No optimum of SOC corresponding to a fraction of the clay content is found, contrary to the theory of “complexed organic carbon” (Dexter et al., 2008). However, the SOC:clay ratio decreases with decreasing soil structure quality. The SOC:clay ratio of 1:8 is the average for a very good structure quality. A SOC:clay ratio of 1:10 is the limit between good and medium structural quality, thus it constitutes a reasonable goal for soil management by farmers. A SOC:clay ratio of 1:8 or smaller leads to a high probability of poor structural state. These ratios can be used as criteria for soil structural quality and SOC management, and in that context, the concept of complexed organic carbon appears relevant.

红壤退化地森林恢复后土壤有机碳对土壤水库库容的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 红壤退化地森林恢复后土壤有机碳对土壤水库库容的影响 DOI: 10.5846/stxb201608041609 作者: 作者单位: 南昌工程学院,南昌工程学院,南昌工程学院,南昌工程学院,南昌工程学院,南昌工程学院,南昌工程学院,南昌工程学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目（31160179）；江西省自然科学基金资助项目（20151BAB204033）；江西省水利厅科技资助项目（KT201546）；江西省高等学校“十二五”水土保持与荒漠化防治重点学科培育基金资助项目 Effects of soil organic carbon on soil reservoir capacity after forest restoration in degraded red soil Author: Affiliation: Nanchang Institute of Technology,,,,,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:亚热带红壤侵蚀退化地实施生态恢复后生物生产力恢复迅速，但土壤尤其是土壤水库的功能并未获得同步恢复，导致土壤水库对于降水和地表径流的调节能力低下，区域性洪涝灾害和季节性干旱依然突出。采用野外调查和室内分析相结合的方式，研究了南方红壤侵蚀退化地典型植被恢复类型（马尾松与阔叶树复层林、木荷与马尾松混交林、阔叶混交林）0-60cm土层土壤水库各种库容差异，以及土壤总有机碳和活性有机碳密度分布特征，采用典型相关分析方法对土壤水库库容与土壤有机碳密度两组指标进行相关分析。结果表明：随着土层深度的增加，各森林恢复类型死库容呈上升趋势，兴利库容和最大有效库容呈下降趋势，防洪库容变化趋势不明显，木荷与马尾松混交林兴利库容略高。不同森林恢复类型同一土层土壤总有机碳密度均表现为马尾松与阔叶树复层林 > 木荷与马尾松混交林 > 阔叶混交林，而活性有机碳密度则以阔叶混交林最大。典型相关分析表明，土壤有机碳水平对土壤水库库容的增加具有显著的因果影响关系（P=0.01），其中对有机碳水平起到主导性贡献作用的是水溶性有机碳。因此，对于退化红壤地森林恢复初期，可通过适当密植和立体种植，提高林地生物量和土壤碳密度，并在马尾松等先锋树种针叶林分中补植阔叶乔灌木，以增加土壤活性有机碳含量，增大土壤水库容量，从而有利于土壤水库结构和功能以及退化生态系统的快速恢复。 Abstract:In a degraded red soil in subtropical China, the soil reservoir did not show a synchronized recovery with the rapid increase of biomass, resulting in frequent floods and droughts at the regional scale. The aim of this study was to determine the changes in soil organic carbon and soil reservoir capacity and their relationship following afforestation. Based on field investigations and lab assays, the differences of soil reservoir capacity in the 0-60 cm soil layer and the distribution characteristics of total organic carbon density and active organic carbon density were studied in three typical types of forest restoration in southern degraded red soil, i.e. Pinus massoniana and broad-leaved tree multiple layer forest(PB), Schima superba-Pinus massoniana mixed forest(SP), and broad-leaved mixed forest(BF). The correlation between soil reservoir capacity and soil organic carbon density was also analyzed using a canonical correlation analysis model. The results showed that with increased soil depth, all three forest restoration types exhibited growth trends in soil invalid capacity, while the storage capacity and the flood control capacity showed downward trends. However, the trend of flood control capacity was not obvious. Additionally, the storage capacity in the SP was higher than that in other forests. The total organic carbon density in the same layers was ranked as follows:PB > SP > BF. The active organic carbon density was largest in BF, suggesting that BF was propitious to the accumulation of active organic carbon. The soil organic carbon was positively correlated with soil reservoir capacity (P=0.01), and soil dissolved organic carbon played the dominant role for the increase of organic carbon levels. As a result, we could develop close-planting and stereoscopic planting appropriately to improve plant biomass and soil carbon density, and then interplant broad-leaved species with pioneer coniferous tree species such as Pinus massoniana at the early stage of forest restoration in degraded red soil. This strategy can increase the active soil organic carbon content and enhance soil reservoir capacity, which is conducive to the rapid recovery of the eroded soil and ecosystem. 参考文献 相似文献 引证文献

Spatial distribution of plant communities and environmental interpretation in Xinjiang Bayanbulak marsh

为探明巴音布鲁克高寒沼泽湿地植物群落与环境因子的关系，采用样线与样方结合的方法，于2014-2015年在天鹅湖沼泽湿地进行植物群落调查与环境因子测定.结果显示，巴音布鲁克天鹅湖沼泽湿地植物共有35种，隶属于19科27属.方差分析表明，地表积水条件显著影响植物群落物种多样性，随着地表积水减少，物种丰富度和Shannon-Wiener指数呈现上升趋势，Pielou指数呈现下降趋势，说明随着地表积水的减少，植物群落的物种多样性逐渐增加.冗余分析与偏冗余分析表明，所有环境因子共解释了植物群落物种组成变异的67.9%.水位与土壤全氮含量对物种组成的总效应达到显著水平，土壤全氮含量的净效应达到极显著水平，但全磷含量和有机碳含量的总效应与净效应均未达到显著水平.研究表明，积水条件和土壤氮含量是巴音布鲁克天鹅湖沼泽湿地植物群落物种组成和分布的主要环境驱动因子.;In order to explore the relationships between the vegetation and environmental factors in Bayanbulak Swan Lake alpine wetland, vegetation survey was conducted and environmental factors, including water table (WT), total nitrogen content (TN), soil organic carbon(SOC), and total phosphorus (TP), were measured in 2014 and 2015. The results showed that a total of 35 plant species belonging to 19 families and 27 genera were identified in Bayanbulak Swan Lake alpine wetland. One-way ANOVA revealed that species composition and richness were significantly affected by the surface water level. Species richness and Shannon-Wiener index increased, and the Pielou index decreased with the decreasing of surface water level. The RDA and partial RDA analyses revealed that four environmental variables totally explained 67.9% of total variations in species composition, of which the gross effects of WT and TN on species composition were significant and the net effect of TN was also significant. However, the gross and net effects of SOC and TP was not significant. Overall, our results indicate that WT and TN are two important determinants of the vegetation composition and its distribution in Bayanbulak Swan Lake alpine wetland.

Ecological stoichiometry controls the transformation and retention of plant-derived organic matter to humus in response to nitrogen fertilisation

Carbon (C) sequestration in soils is a means for increasing soil organic carbon (SOC) stocks and is a potential tool for climate change mitigation. One recommended management practice to increase SOC stocks is nitrogen (N) fertilisation, however examples of positive, negative or null SOC effects in response to N addition exist. We evaluated the relative importance of plant molecular structure, soil physical properties and soil ecological stoichiometry in explaining the retention of SOC with and without N addition. We tracked the transformation of 13C pulse-labelled buffel grass (Cenchrus ciliaris L.), wheat (Triticum aestivum L.) and lucerne (Medicago sativa L.) material to the <53 μm silt + clay soil organic C fraction, hereafter named “humus”, over 365-days of incubation in four contrasting agricultural soils, with and without urea-N addition. We hypothesised that: a) humus retention would be soil and litter dependent; b) humus retention would be litter independent once litter C:N ratios were standardised with urea-N addition; and c) humus retention would be improved by urea-N addition. Two and three-way factorial analysis of variance indicated that 13C humus was consistently soil and litter dependent, even when litter C:N ratios were standardised, and that the effect of urea-N addition on 13C humus was also soil and litter dependent. A boosted regression analysis of the effect of 44 plant and soil explanatory variables demonstrated that soil biological and chemical properties had the greatest relative influence on 13C humus. Regression tree analyses demonstrated that the greatest gains in 13C humus occurred in soils of relatively low total organic C, dissolved organic C and microbial biomass C (MBC), or with a combination of relatively high MBC and low C:N ratio. The greatest losses in 13C humus occurred in soils with a combination of relatively high MBC and low total N or increasing C:N ratio. We conclude that soil variables involved in soil ecological stoichiometry exert a greater relative influence on incorporating organic matter as humus compared to plant molecular structure and soil physical properties. Furthermore, we conclude that the effect of N fertilisation on humus retention is dependent upon soil ecological stoichiometry.

Impacts of snow and organic soils parameterization on northern Eurasian soil temperature profiles simulated by the ISBA land surface model

Abstract. In this study we analyzed how an improved representation of snowpack processes and soil properties in the multilayer snow and soil schemes of the Interaction Soil-Biosphere-Atmosphere (ISBA) land surface model impacts the simulation of soil temperature profiles over northern Eurasian regions. For this purpose, we refine ISBA's snow layering algorithm and propose a parameterization of snow albedo and snow compaction/densification adapted from the detailed Crocus snowpack model. We also include a dependency on soil organic carbon content for ISBA's hydraulic and thermal soil properties. First, changes in the snowpack parameterization are evaluated against snow depth, snow water equivalent, surface albedo, and soil temperature at a 10 cm depth observed at the Col de Porte field site in the French Alps. Next, the new model version including all of the changes is used over northern Eurasia to evaluate the model's ability to simulate the snow depth, the soil temperature profile, and the permafrost characteristics. The results confirm that an adequate simulation of snow layering and snow compaction/densification significantly impacts the snowpack characteristics and the soil temperature profile during winter, while the impact of the more accurate snow albedo computation is dominant during the spring. In summer, the accounting for the effect of soil organic carbon on hydraulic and thermal soil properties improves the simulation of the soil temperature profile. Finally, the results confirm that this last process strongly influences the simulation of the permafrost active layer thickness and its spatial distribution.

THE USE OF PATH ANALYSIS IN THE DETERMINATION OF ENVIRONMENTAL FACTOR EFFECTS ON THE TOTAL PRODUCTION OF AQUACULTURE PONDS IN PASURUAN, EAST JAVA PROVINCE

Environmental factors in the form of soil and water quality are the important factors of aquaculture pond productivity, including total production (tiger shrimps, Penaeus monodon, and milkfish, Chanos chanos) in Pasuruan, East Java Province. The objective of this study was to analyze the direct or indirect effects of soil and water quality on the total production of ponds in Pasuruan using a path analysis application. Data were collected in the pond areas around Pasuruan Regency including Nguling, Lekok, Rejoso, Keraton, and Bangil Sub-Districts as well as Pasuruan City. Soil quality was determined as a free variable and exogen; water quality as mediate variable, suspended, and endogen; as well as milkfish production as suspended variable and endogen. Environmental characteristics were illustrated using descriptive statistics, while environment factor effects on total production were analyzed using path analysis. The results of path analysis show that from the 12 analyzed soil quality variables, only two variables were affected in the total production of pond (tiger shrimps and milkfish) namely: contents of soil organic carbon and soil phosphate. While based on 11 water quality variables, two variables (water salinity and water iron) were affected the total production of ponds in Pasuruan Regency. The direct effects of soil organic carbon and phosphate on the total production were 0.314 and -0.600, respectively. Water salinity and water iron gave direct effects on total production amounting to -0.678 and 0.358 respectively. It is also found that two soil variables which were affected in the total production, did not indicate the effect towards water quality in ponds. Further implication of this research is put more attention for these variables into pond’s management in order to gain more production. Technical application could be appropriate for pond preparation and frequently water changing during grow out.

Biochar impact on nitrate leaching as influenced by native soil organic carbon in an Inceptisol of central India

Biochar is anticipated to be an effective mitigation option to nitrate leaching. However, the extent to which its effectiveness is influenced by native soil organic carbon (SOC) is not known. Thus, the present study was conducted to investigate the interactive effect of native SOC and biochar amendment on leaching of nitrate and total dissolved salts (TDS) using a laboratory column experiment. The study was conducted in a loamy (Mixed Hyperthermic Udic Ustocrept) soil of central India, with three native SOC levels, four levels of biochar amendment, and three replications, in a factorial design. The three native total SOC levels were 1.18% (C1), 0.97% (C2) and 0.79% total SOC (C3) and four biochar amendment levels were 0 (B0, control), 5 (B5), 10 (B10) and 20 (B20) g biochar kg−1 of air dry soil. Repacked soil columns (40cm height and 11cm internal diameter) were leached with deionized water once a week for 15 consecutive weeks. Nitrate in form of KNO3 was added at the rate equivalent to 100mgkg−1 soil (220kgha−1) at each application in the 1st, 9th and 12th week. Leaching of NO3−-N and TDS significantly reduced with increase in native SOC content (p<0.01) and increase in amount of biochar (p<0.01) amendment. However, interaction effect was significant only for the TDS flux. At higher SOC content, leaching of NO3 - N and TDS of the leachate were significantly lower. As compared to C1 soil, total NO3−-N leached in C3 soil was higher by 40, 45, 37 and 11% under B0, B5, B10 and B20 biochar amendment levels indicating biochar application at the rate of 20gkg−1 soil (B20) could mitigate nitrate leaching by 29% in the low carbon (C3) soil. Differential behaviour of biochar at different SOC level was observed with regard to NO3−-N and TDS leaching. The effectiveness of higher dose of biochar (B20) in mitigating NO3− leaching was higher in soils with low SOC level. The best biochar treatment (B20) could reduce NO3−-N leaching by 14% under C1, as compared to 23 and 32% under C2 and C3 soils. Increased sorption and water retention under high biochar treatments might be responsible for reduced NO3 leaching.

Priming effect of bamboo (Phyllostanchys edulis Carrière) biochar application in a soil amended with legume

Biochar application to soils can mitigate carbon dioxide (CO2) by increasing soil carbon (C) sink, but also causes increased CO2 released from soils through priming effects of soil organic carbon (SOC). However, priming effects of biochar application on SOC are complex, showing inconsistent results, and further complicated when applied with other substrates such as organic amendment (OA). Incubation experiments were conducted using Typic Durudand with bamboo (Phyllostanchys edulis Carrière) biochar (400°C) and OA (crotalaria) applied individually, simultaneously or with biochar applied 5 weeks prior to OA application. After 56 d of incubation, cumulative CO2 released from soils with no amendments (control), biochar only (BC), OA only (OA), simultaneous (BC+OA), and differently timed (BCP+OA) applications reached 313, 326, 1270, 1535 and 1311 mg CO2 kg−1, respectively. The OA application distinctly increased CO2 released from the soils due to its decomposition. The OA decomposition rates were comparable with OA and BC+OA, while those with BCP+OA were lower than those with other treatments during early incubation. Net CO2 (CO2-(treatment) − CO2-control) from soils with BC, OA, BC+OA and BCP+OA yielded 13, 957, 1222 and 998 mg CO2 kg−1, respectively. Primed CO2-BC of 13 mg CO2 kg−1 was equivalent to 4.2% of priming effect relative to CO2-control. Primed CO2-BC+OA [net CO2-BC+OA − (net CO2-BC + net CO2-OA)] and primed CO2-BCP+OA were 252 and 28 mg CO2 kg−1, equivalent to 26% and 2.9% of priming effects relative to sum of net CO2-BC + net CO2-OA, respectively. The priming effect with BC was negligible likely because of limited amounts of biochar labile C to induce co-metabolism, while BC+OA showed a modest priming effect most likely as a result of co-metabolism induced by additional mineralization of presumably SOC and/or biochar, because the OA decomposition rates were not affected by biochar application. The priming effect with BCP+OA was comparable to that with BC likely due to changes in soil properties caused by biochar application prior to OA, likely from slowed decomposition rates of OA.